In past 4 years, the Pathology Core has committed to 1) recruit more users from NHLBI and NIH campus wide, including FDA laboratories, and 2) improve our abilities for better customer services. Currently, we have about 90 users from 51 Laboratories/ PIs and have more than 280 histopathology requests, annually. The numbers of Core user and Laboratory/PI are steadily growing. In addition to NHLBI laboratories, we have services for 20 laboratories and PIs from 10 Non-NHLBI users. We make more than 20,000 histology slides, including about 5,500 frozen slides, annually. Among these, we have made 3,4004,000 routine H&E stained slides and more than 1,000 special staining slides, includes Masson trichrome, PAS, elastic and Oil-red O staining. We can also perform about 300 immunohistochemstry slides with either peroxidase-DAB or fluorescence labelings. For customer service, Core staff are working closely with users to find out what they need. We then modify our procedures to meet their goal. We can perform special embedding, make different orientations, special section cut, includes serial sections, step sections and selective sections mounting. Core staff have increased knowledge and experiences to recognizes tissue characteristics for specific interesting reasons, even on unstained slides. We also increased our staining ability. Initially, the Pathology Core provide routine H&E stain, and several special histology staining procedures, such as Masson, PAS, EVG, von Kossa, PAM, Diff- Quick and Oil-red O stainings. Recent years, due to the increasing user demand, we have introduced or modified 8 more staining methods. Now, we can offer 15 protocols. In addition to the above, we provide Alcian blue, Alizarin red, Toluidine blue, Movat, Prussian blue, Picro-sirius red, Nissl and TTC stains. For immunostaining procedures, we can perform peroxidase-DAB, Alkaline phosphate, immuno- fluorescence procedures. We can adjust for different primary antibodies, on various tissues/organs and for double, triple labeling, including special procedures, such as immunofluorescent-labeling for super resolution microscope. Diagnostic histopathology. Core head is involved in the services for histo-pathological analysis and immunostaining. We can do histo-pathological interpretation, histology evaluations with score systems and development of final images for publications. These efforts resulted in 8 publications in 20162017. The Pathology Core offers training for cutting frozen/paraffin sections, immunohistochemistry procedures and histology microphotograph by using Core bright field microscope equipped with digital camera. Currently, we have 14 users of the Leica DMB-4000 microscope and 11 of the Cryo- stat (frozen sections). Since the new NanoZoomer scanner was installed, we have trained 31 users, who have used the scanner for a combined total of 300 hours, annually. In addition, our Auto-stainer, antigen retrieval microwave oven and Immunostaining bench is open to Core users for their de- paraffin and immunohistochemistry procedures. We provide most reagents for the procedures except primary antibodies. We have had 8 scientists from 4 Laboratories as users during this period. The Pathology Core continues to offer users free consultations on their experimental procedures, technical concerns and morphology evaluations, and training on histology instruments. Our Core not only provides service for NHLBI DIR laboratories, we are also open to NIH campus wide for their histology needs. For FY2017, we have users from 10 different institutes other than NHLBI, who sent requests to us because of customer services, quality, convenience and low costs.